In electrophotography, a latent image is created on the surface of an imaging member such as a photoconducting material by first uniformly charging the surface and then selectively exposing areas of the surface to light. A difference in electrostatic charge density is created between those areas on the surface which are exposed to light and those areas on the surface which are not exposed to light. The latent electrostatic image is developed into a visible image by electrostatic toners. The toners are selectively attracted to either the exposed or unexposed portions of the photoconductor surface, depending on the relative electrostatic charges on the photoconductor surface, the development electrode and the toner.
Typically, a dual layer electrophotographic photoconductor comprises a substrate such as a metal ground plane member on which a charge generation layer (CGL) and a charge transport layer (CTL) are coated. The charge transport layer contains a charge transport material which comprises a hole transport material or an electron transport material. For simplicity, the following discussions herein are directed to use of a charge transport layer which comprises a hole transport material as the charge transport compound. One skilled in the art will appreciate that if the charge transport layer contains an electron transport material rather than a hole transport material, the charge placed on a photoconductor surface will be opposite that described herein.
When the charge transport layer containing a hole transport material is formed on the charge generation layer, a negative charge is typically placed on the photoconductor surface. Conversely, when the charge generation layer is formed on the charge transport layer, a positive charge is typically placed on the photoconductor surface. Conventionally, the charge generation layer comprises the charge generation compound or molecule, for example a squaraine pigment, a phthalocyanine, or an azo compound, alone or in combination with a binder. The charge transport layer typically comprises a polymeric binder containing the charge transport compound or molecule. The charge generation compounds within the charge generation layer are sensitive to image-forming radiation and photogenerate electron-hole pairs therein as a result of absorbing such radiation. The charge transport layer is usually non-absorbent of the image-forming radiation and the charge transport compounds serve to transport holes to the surface of a negatively charged photoconductor. Photoconductors of this type are disclosed in the Adley et al U.S. Pat. No. 5,130,215 and the Balthis et al U.S. Pat. No. 5,545,499.
Allen et al., U.S. Pat. No. 5,322,755, teach a layered polyconductive imaging member comprising a substrate, a photogenerator layer and a charge transport layer. Allen et al. teach the photogenerator layer comprises a binder mixture of two or more polymers such as polyvinylcarbazole, polycarbonates, polyvinylbutyral and polyesters.
Nogami et al., U.S. Pat. No. 5,725,982, teach photoconductors comprising a charge transport layer comprising an aromatic polycarbonate resin. Nogami et al. further teach the photoconductor may comprise a charge generating layer comprising resins such as polycarbonate resin, polyvinylbutyral, polyacrylic ester, polymethacrylic ester, vinyl-chloride based copolymer, polyvinylacetal, polyvinylpropional, phenoxy resin, epoxy resin, urethane resin, cellulose ester and cellulose ether.
Nakamura et al., U.S. Pat. No. 5,837,410, teach a photoconductor comprising a conductive layer and an organic film. Nakamura et al. teach that the organic film may comprise a charge-generating layer which comprises binders such as polyvinylbutyral resin, polyvinylchloride copolymer resin, acrylic resin, polyester resin and polycarbonate resin and a charge transport layer comprising resins such as polyester resin, polycarbonate resin, polymethacrylic resin and polystyrene resin.
Polyarylether ketones can be synthesized in art recognized ways, such as the method taught by Kelsey, U.S. Pat. No. 4,882,397, Rose, U.S. Pat. No. 4,419,486, and Roovers et al., U.S. Pat. No. 5,288,834. Kelsey teaches a process for preparing polyarylether ketones from a polyketal. Rose teaches sulfonation of polyarylether ketones. Roovers et al. teach bromomethyl derivatives of polyarylether ketones are useful intermediates for further functionalizing the aromatic polyether ketones, and further teach functionalized polyarylether ketones such as carbonyl fluoride poly (aryl ether ether ketone), cyan methylene poly(aryl ether ether ketone), diethylamine methylene poly(aryl ether ether ketone), and aldehyde polyaryl (aryl ether ether ketone).
Nakamura et al., EP 0501455 A1, teach a photoconductor comprising a substrate and a photosensitive layer comprising a charge generating layer and a charge transporting layer. Nakamura et al. teach the charge generating layer contains an organic pigment and a polyarylether ketone binder resin.
Japanese Patent Application JP 63239454 A teaches an electrophotographic sensitive body comprising a layer containing a polyetherketone binder resin, while Japanese Patent Application JP 632247754 A teaches an electrophotographic sensitive body comprising a charge transfer layer comprising a hydrazone compound charge transfer material and a polyetherketone resin. Japanese Application JP 63070256 A teaches a photoconductive layer comprising a polyetherketone resin laminated on a conductive base.
Kan et al., U.S. Pat. No. 4,772,526, disclose a reusable electrophotographic imaging element having a photoconductive surface layer in which the binder resin comprises a block copolyester or copolycarbonate having a fluorinated polyether block. Kan et al. teach that the surface layer is either capable of generating an injecting charge carriers upon exposure, or capable of accepting and transporting injected charge carriers.
Muller, U.S. Pat. No. 5,006,443, discloses perfluoralkyl group-containing polymers which are useful in radiation-sensitive reproduction layers. Muller teaches the perfluoroalkyl group-containing polymers comprise polymers or polycondensates and have phenolic hydroxyl groups and perfluoroalkyl groups which are optionally attached through intermediate members.
Ishikawa et al., U.S. Pat. No. 5,073,466, disclose an electrophotographic member comprising a support, a photoconductive layer, and a surface layer comprising a lubricating agent and a fixing group. Ishikawa et al. teach the lubricating agent has a perfluoropolyoxyalkyl group or a perfluoropolyoxyalkylene group.
Suzuki, et al., U.S. Pat. No.5,344,733, disclose an electrophotographic receptor having an overcoat layer on the surface of a photosensitive layer containing a charge generating substance. Suzuki et al. teach the overcoat layer comprises a fluororesin cured with a melamine compound or an isocyanate compound as a cross-linking agent, a charge generating substance, and a charge transport substance.
The charge transport layer and charge generation layers of photoconductors generally comprise binders. For example, the charge generation layer generally comprises pigments, however, since pigments do not adhere effectively to metal substrates, polymer binders are usually included. Unfortunately, the electrical sensitivity of the charge generation layer, drum wear, or composition pot-life can be affected by the polymer binder.
For example, the use of polyvinylbutyral as a charge generation layer binder is advantageous in that it significantly improves adhesion of the charge generation layer to the substrate. Unfortunately, polyvinylbutyral can disadvantageously affect electrical characteristics of the resulting photoconductor in causing, inter alia, high dark decay and residual voltage properties.
Polycarbonates have been known to improve the mechanical properties of a photoconductor, particularly its impact resistance. Unfortunately, the use of polycarbonates can result in photoconductors which are susceptible to drum-end wear, which may result in print-quality defects or drum failure, and to scratches in the paper area, which may lead to print-quality defects.
The use of polytetrafluoroethylene results in photoconductor drums exhibiting lower coefficients of friction and higher abrasion resistance. Unfortunately, polytetrafluoroethylene tends to settle in the transport composition, therefore adversely affecting the pot-life of the composition.